Hybrid cascading lubrication and cooling system

ABSTRACT

A hybrid cascading lubrication and cooling system ( 200, 400 ) for an electrical machine ( 102 ) with nested stages is provided. The electrical machine ( 102 ) includes an inner nested stage ( 444 ) nested with respect to an outer nested stage ( 446 ). An oil pump ( 222 ) is coupled to an oil pump inlet tube ( 226 ) to draw oil from an oil sump ( 224 ), and a cooling core ( 230 ) to distribute pumped oil within the electrical machine ( 102 ). A rotor member ( 212 ) is coupled to the inner nested stage ( 444 ) and the outer nested stage ( 446 ). The rotor member ( 212 ) centrifugally pumps oil from the cooling core ( 230 ) through inner radial holes ( 424 ) and outer radial holes ( 436 ) in the rotor member ( 212 ) upon rotation about a central axis ( 216 ) of the electrical machine ( 102 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/502,492, filed Jul. 14, 2009, entitled HYBRID CASCADINGLUBRICATION AND COOLING SYSTEM and which is hereby incorporated byreference in its entirety.

This application contains subject matter related to the subject matterof U.S. patent application Ser. No. 12/486,365 (now U.S. Pat. No.7,923,874) entitled NESTED TORSIONAL DAMPER FOR AN ELECTRIC MACHINE andU.S. patent application Ser. No. 12/499,292, entitled NESTED EXCITER ANDMAIN GENERATOR STAGES FOR A WOUND FIELD GENERATOR, which are assigned tothe same assignee as this application, Hamilton Sundstrand Corporationof Windsor Locks, Connecticut and which are hereby incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein generally relates to lubrication andcooling of electrical machines, and more particularly to hybridcascading lubrication and cooling for an electrical machine with nestedstages.

An electrical machine may include one or more stages arrangedsequentially along a shaft as a rotor assembly. To cool the electricalmachine, cooling oil can be pumped into the inside diameter of theshaft. The cooling oil flows through the rotor assembly to remove heat.The cooling oil can be pressurized and sprayed directly from the shaftto cool components in close physical proximity to the shaft. However,such a cooling and lubrication scheme may be ineffective if cooling oilcannot be pumped through the shaft or components to be cooled are notdirectly reachable by spray from the shaft.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a hybrid cascading lubricationand cooling system for an electrical machine with nested stages isprovided. The electrical machine includes an inner nested stage and anouter nested stage, where the inner nested stage is radially nestedabout a central axis of the electrical machine with respect to the outernested stage. The hybrid cascading lubrication and cooling systemincludes an oil pump coupled to an oil pump inlet tube to draw oil froman oil sump, and a cooling core to distribute pumped oil within theelectrical machine. A rotor member is coupled to the inner nested stageand the outer nested stage of the electrical machine. The rotor membercentrifugally pumps oil from the cooling core through inner radial holesand outer radial holes in the rotor member upon rotation about thecentral axis of the electrical machine.

According to yet another aspect of the invention, a method for producinga hybrid cascading lubrication and cooling system for an electricalmachine with nested stages is provided. The electrical machine includesan inner nested stage and an outer nested stage, where the inner nestedstage is radially nested about a central axis of the electrical machinewith respect to the outer nested stage. The method includes coupling anoil pump to an oil pump inlet tube to draw oil from an oil sump, andconfiguring a cooling core to distribute pumped oil within theelectrical machine. The method additionally includes coupling a rotormember to the inner nested stage and the outer nested stage of theelectrical machine. The rotor member is configured to centrifugally pumpoil from the cooling core through inner radial holes and outer radialholes in the rotor member upon rotation about the central axis of theelectrical machine.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 illustrates an exemplary embodiment of a driveline system thatincludes an electrical machine installed in the driveline system;

FIG. 2 depicts a cut-away view of an exemplary embodiment of a hybridcascading lubrication and cooling system for an electrical machine withnested stages;

FIG. 3 illustrates a profile view of an exemplary embodiment ofintegrated tubing in an electrical machine;

FIG. 4 illustrates a cut-away view of an exemplary embodiment of ahybrid cascading lubrication and cooling system for an electricalmachine with nested stages; and

FIG. 5 depicts a process for producing a hybrid cascading lubricationand cooling system for an electrical machine with nested stages.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an exemplary embodiment of a driveline system 100. Inan exemplary embodiment, the driveline system 100 is part of aland-based vehicle driveline, such as a truck or a tank. The drivelinesystem 100 includes an electrical machine 102 inserted between an engine104 and a transmission 106. In an exemplary embodiment, the electricalmachine 102 has coupling points 108 that align with existing couplingpoints on the engine 104 and transmission 106. Thus, the impact onexisting components, such as the engine 104 and transmission 106, can beminimized when the electrical machine 102 is inserted into the drivelinesystem 100. While the electrical machine 102 is depicted between theengine 104 and transmission 106, it will be understood that thearrangement of components on the driveline system 100 is not so limited.For instance, there may be additional components, such as a clutchinserted in the driveline system 100, or the electrical machine 102 maybe coupled to the opposite end of the transmission 106 if a smallerdiameter is desired for the electrical machine 102. The electricalmachine 102 may be a generator or alternator for producing electricalcurrent and voltage responsive to mechanical rotation.

In an exemplary embodiment, the electrical machine 102 is coupled toexternal tubing 110 to route oil to and from a heat exchanger/reliefvalve/filter assembly (ERFA) 112. Oil that circulates through theelectrical machine 102 draws heat generated by the electrical machine102 and also lubricates components of the electrical machine 102. Theoil in the electrical machine 102 may also capture particulate matterand other debris from within the electrical machine 102. One or morepumps circulate the oil through the external tubing 110 to the ERFA 112,where the oil is cooled and filtered prior to returning to theelectrical machine 102.

FIG. 2 depicts a cut-away view of an exemplary embodiment of a hybridcascading lubrication and cooling system 200 for the electrical machine102 of FIG. 1. In the exemplary embodiment of the electrical machine 102depicted in FIG. 2, the electrical machine 102 is a nested wound fieldgenerator with an outer stage stator 202, a outer stage rotor 204, arotating rectifier assembly 206, an inner stage stator 208, and an innerstage rotor 210. The outer stage rotor 204 and the inner stage rotor 210are coupled to a rotor member 212, which is driven by the rotation ofdriveshaft 214. In an exemplary embodiment, the driveshaft 214 rotatesabout a central axis 216 of the electrical machine 102, causing therotor member 212 to rotate. The outer stage stator 202 and inner stagestator 208 remain stationary as the rotor member 212 rotates. Therotating rectifier assembly 206 may be located in close proximity to theouter stage rotor 204 or the inner stage rotor 210 on the rotor member212, and electrically coupled to both the outer stage rotor 204 and theinner stage rotor 210. A wire cover 218 may be used to hold wiring insupport of the rotating rectifier assembly 206.

As the driveshaft 214 rotates, the rotor member 212 rotates the innerstage rotor 210 in close proximity to the inner stage stator 208, andthe outer stage rotor 204 rotates in close proximity to the outer stagestator 202. Applying a DC source, such as current from a battery oralternator (not depicted), to the inner stage stator 208 results in a DCfield to establish field communication inducing an alternating currentin the inner stage rotor 210 as the rotor member 212 rotates. Thealternating current in the inner stage rotor 210 flows through therotating rectifier assembly 206 to produce a direct current in the outerstage rotor 204. The direct current in the outer stage rotor 204 createsa DC field to establish field communication inducing an alternatingcurrent in the outer stage stator 202 as the rotor member 212 rotates.The AC in the outer stage stator 202 can be converted to DC via anexternal output rectifier assembly. Thus, the electrical machine 102 canconvert the mechanical rotation of the driveshaft 214 into a highvoltage DC power source.

As can be seen in FIG. 2, the outer stage stator 202, outer stage rotor204, inner stage stator 208, and inner stage rotor 210 are arrangedconcentrically about the central axis 216, such that the inner stagestator 208 and the inner stage rotor 210 are radially nested about thecentral axis 216 of the electrical machine 102 with respect to the outerstage stator 202 and the outer stage rotor 204. This configurationresults in a minimal impact to the overall length of the drivelinesystem 100 of FIG. 1 when the electrical machine 102 is inserted betweenthe engine 104 and the transmission 106 and attached at coupling points108.

The sequence in which nested rotors and stators as nested stages arespaced extending from the driveshaft 214 can vary within the scope ofthe invention. For example, the radial distance between the inner stagerotor 210 and the central axis 216 may be less than the radial distancebetween the inner stage stator 208 and the central axis 216 as depictedin FIG. 2. As an alternate configuration, the radial distance betweenthe inner stage rotor 210 and the central axis 216 can be greater thanthe radial distance between the inner stage stator 208 and the centralaxis 216, for instance, reversing the relative position of the innerstage stator 208 and the inner stage rotor 210 depicted in FIG. 2. Insimilar fashion, the radial distance between the outer stage rotor 204and the central axis 216 can be less than the radial distance betweenthe outer stage stator 202 and the central axis 216 as depicted in FIG.2. Conversely, the radial distance between the outer stage rotor 204 andthe central axis 216 may be greater than the radial distance between theouter stage stator 202 and the central axis 216.

To cool and lubricate components of the electrical machine 102, a hybridcascading lubrication and cooling system 200 is integrated in theelectrical machine 102. An oil pickup tube 220 draws oil responsive tooil pump 222 from oil sump 224. Oil is drawn up oil pump inlet tube 226to the oil pump 222 and continues to oil pump outlet tube 228. The oilmay flow from the oil pump outlet tube 228 to the ERFA 112 of FIG. 1 viathe external tubing 110, where heat is extracted from the oil and theoil is filtered. The cooled and filtered oil returns to the electricalmachine 102 for distribution in cooling core 230. Centrifugal pumpingaction of the rotor member 212 rotating drives the oil throughout theelectrical machine 102. While only a single oil pump 222 is depicted inFIG. 2, multiple instances of the oil pump 222 can be utilized forredundancy and to keep the size of each oil pump 222 compact. Varioustypes of pumps, such as vane, piston, or centrifugal positivedisplacement pumps, can be used to implement the oil pump 222.Furthermore, internally or externally integrated primary pumps orseparate pumps can be used to move oil from the oil sump 224 to the ERFA112 of FIG. 1.

Alternate embodiments of the electrical machine 102 include permanentmagnet, induction, and switched reluctance generators and/or motors. Inthese alternate embodiments, one or more of the outer stage stator 202,outer stage rotor 204, rotating rectifier assembly 206, inner stagestator 208, and/or inner stage rotor 210 can be eliminated or replacedwhile still maintaining nested stages of the electrical machine 102. Forexample, the rotor member 212 may enable nesting of two separatepermanent magnet generators on the driveshaft 214, where the hybridcascading lubrication and cooling system 200 provides lubrication andcooling.

FIG. 3 illustrates a profile view of an exemplary embodiment ofintegrated tubing in the electrical machine 102. As can be seen in FIG.3, two oil pumps 222 can draw oil from the oil sump 224 using oil pickuptube 220 branching to two oil pump inlet tubes 226. The oil pumps 222are positive-displacement pumps that may be driven off of the driveshaft214 of FIG. 2 via gearing to lift the oil from the oil sump 224, andpump it to the ERFA 112 of FIG. 1. Oil flows from each oil pump 222 to arespective oil pump outlet tube 228 to a port 302, which combines theoil flow for the ERFA 112 of FIG. 1. Oil returning from the ERFA 112 ofFIG. 1 is received at the cooling core 230 of FIG. 2, where it isdistributed within the electrical machine 102, eventually returning tothe oil sump 224.

FIG. 4 illustrates a hybrid cascading lubrication and cooling system 400for electrical machine 102. The hybrid cascading lubrication and coolingsystem 400 represents a detailed view of an embodiment of the hybridcascading lubrication and cooling system 200 of FIG. 2. As isillustrated in FIG. 4, oil enters the electrical machine 102 at port 402into cooling core 230 for distribution. Oil may be received at the port402 from the ERFA 112 of FIG. 1. A portion of the oil in the coolingcore 230 flows to port 404 to cool a heat exchanger 406 of theelectrical machine 102, and the oil then proceeds back to the oil sump224 of FIGS. 2 and 3. The oil also flows down the cooling core 230 toports 408 and 410. At port 408, oil exits the cooling core 230 and issprayed onto bearing 412, gear 414, and into centrifugal reservoir 416that supplies bearing 418 with oil. The gear 414 may be used to driveone or more oil pump 222 of FIGS. 2 and 3.

The bearings 412 and 418 enable the electrical machine 102 to beself-supporting. In an alternate embodiment, a crankshaft in the engine104 of FIG. 1 is directly coupled to the rotor member 212, where therotor member 212 acts as a flywheel for the engine 104. In thisembodiment, bearings 412 and 418 can be omitted, as crankshaft bearingsin the engine 104 may be sufficient to support rotation of the rotormember 212. The outer stage stator 202 and the inner stage stator 208can be directly coupled to the engine 104. Thus, if bearings 412 and 418are omitted, oil is not sprayed on the bearings 412 and 418. Such anembodiment may also eliminate the centrifugal reservoir 416.

At port 408, cooling oil leaves the cooling core 230, and is sprayedinto inner stage centrifugal reservoir 420. In the inner stagecentrifugal reservoir 420, the oil is pressurized by centrifugal pumpingaction of the rotor member 212 rotating, and oil is directed to flowacross windings 422 of the inner stage rotor 210 providing cooling oilflow to the inner stage rotor 210. Oil gathers in the inner stagecentrifugal reservoir 420 prior to passing through inner radial holes424 in the circumference of rotor winding retention bands 426 of therotor member 212. Oil also gathers in inner stage centrifugal reservoir428 to cool the inner stage rotor 210.

Oil is sprayed from the inner stage centrifugal reservoir 428 acrosswindings 430 of the inner stage stator 208 to provide a cooling oil flowto the inner stage stator 208. As the oil leaves the inner stage stator208, it is collected by outer stage centrifugal reservoir 432 and outerstage centrifugal reservoir 434. The outer stage centrifugal reservoir432 also receives supplemental cooling oil from the cooling core 230 atport 410. Oil at the outer stage centrifugal reservoir 432 isre-pressurized by centrifugal pumping action of the rotor member 212rotating, prior to flowing through outer radial holes 436 in the rotormember 212. As oil passes through the outer radial holes 436, the oil isdirected to flow across windings 438 of the outer stage rotor 204,providing cooling oil to the outer stage rotor 204.

Oil is trapped in the outer stage centrifugal reservoir 434 prior toleaving the outer stage rotor 204 and spraying on windings 440 of theouter stage stator 202. After oil is sprayed on the windings 440, theoil is forced by gravity back to the oil sump 224 of the electricalmachine 102, as depicted in FIGS. 2 and 3.

The combination of components that enable oil to flow from the oil sump224 to the ERFA 112 of FIG. 1 and distribute the oil within theelectrical machine 102 forms the hybrid cascading lubrication andcooling system 400. However, the ERFA 112 does not need to be includedin the hybrid cascading lubrication and cooling system 400. Oildistribution within the electrical machine 102 uses the centrifugalpumping action of the rotor member 212 rotating to provide motive forceto cause the oil to flow throughout the electrical machine 102. Oildelivered to electrical machine core 442 is collected and passed throughinner radial holes 424 to inner nested stage 444 of the electricalmachine 102. Oil in the inner nested stage 444 is centrifugally pumpedtowards outer nested stage 446, where supplemental oil is added fromport 410 prior to passing through outer radial holes 436 to the outernested stage 446. The inner nested stage 444 may include the inner stagestator 208 and the inner stage rotor 210, and the outer nested stage 446may include the outer stage stator 202 and the outer stage rotor 204.The inner nested stage 444 is radially nested about the central axis 216of the electrical machine 102 with respect to the outer nested stage446. In alternate embodiments, the inner nested stage 444 and the outernested stage 446 can include other field generating components, such asmagnets, rather than using windings. Additionally, the inner nestedstage 444 and the outer nested stage 446 can be electricallyindependent, resulting in separate voltage outputs from the electricalmachine 102.

The flow of oil between the inner stage centrifugal reservoirs 420 and428 and the outer stage centrifugal reservoirs 432 and 434 acts ascascading cooling shelves as oil moves between centrifugal reservoirs.Geometry of the rotor member 212 within the electrical machine 102 formsthe inner stage centrifugal reservoir 420 and the outer stagecentrifugal reservoir 432, which feed the inner radial holes 424 andouter radial holes 436 to centrifugally transfer oil radially outward.The inner radial holes 424 and outer radial holes 436 direct the oilfrom the inner stage centrifugal reservoir 420 and the outer stagecentrifugal reservoir 432 to respective sources of heat for cooling andlubrication.

FIG. 5 depicts a process 500 for producing a hybrid cascadinglubrication and cooling system 400 in an electrical machine with nestedstages, such as the electrical machine 102 of FIGS. 1-4. As previouslydescribed, the inner nested stage 444 is radially nested about centralaxis 216 of the electrical machine 102 with respect to the outer nestedstage 446. The inner nested stage 444 may include inner stage stator 208and inner stage rotor 210. The outer nested stage 446 may include outerstage stator 202 and outer stage rotor 204.

At block 502, oil pump 222 is coupled to oil pump inlet tube 226 to drawoil from oil sump 224. Additional oil pumps 222 can also be useddepending upon the desired flow rate and sizing constraints. Forexample, as depicted in FIG. 3, a second oil pump 222 can be coupled toa second oil pump inlet tube 226 to draw oil from the oil sump 224. Thesecond oil pump outlet tube 228 may be coupled to the second oil pump222. Port 302 of FIG. 3 can be coupled to the oil pump outlet tube 228and the second oil pump outlet tube 228 to combine oil flow from the oilpump 222 and the second oil pump 222 prior to routing the oil flow tothe ERFA 112 of FIG. 1. The cooling core 230 may receive oil returnedfrom the ERFA 112.

At block 504, cooling core 230 is configured to distribute pumped oilwithin the electrical machine 102. Oil can be directed through port 404coupled to the cooling core 230 to cool the heat exchanger 406 of theelectrical machine 102. Oil can also be directed through port 408coupled to the cooling core 230 to cool and lubricate bearing 412 andgear 414 of the electrical machine 102. Port 408 may supply oil tocentrifugal reservoir 416, which in turn supplies bearing 418 with oil.Port 408 can also supply oil to inner stage centrifugal reservoir 420 ofthe inner nested stage 444. Port 410 may also be coupled to the coolingcore 230, where port 410 provides a flow path to combine supplementaloil with oil from the inner nested stage 444 at outer stage centrifugalreservoir 432 of the outer nested stage 446.

At block 506, rotor member 212 is coupled to the inner nested stage 444and the outer nested stage 446. For example, the rotor member 212 can becoupled to the inner stage rotor 210 and the outer stage rotor 204. Therotor member 212 is configured to centrifugally pump oil from thecooling core 230 through inner radial holes 424 and outer radial holes436 in the rotor member 212 upon rotation about the central axis 216 ofthe electrical machine 102. The inner radial holes 424 provide a flowpath for oil from the inner stage centrifugal reservoir 420 through theinner nested stage 444, which can cool and lubricate the inner stagestator 208 and the inner stage rotor 210. The outer radial holes 436provide a flow path for oil from the outer stage centrifugal reservoir432 through the outer nested stage 446, which can cool and lubricate theouter stage stator 202 and the outer stage rotor 204. The rotation ofthe rotor member 212 provides centrifugal pumping force to cascade oilfrom electrical machine core 442 to inner nested stage 444 to outernested stage 446.

As described herein, the hybrid cascading lubrication and cooling system400 produced via process 500 of FIG. 5 is integrated in electricalmachine 102. The electrical machine 102 can be connected inline ondriveline system 100 via coupling points 108, for instance, to couplethe electrical machine 102 to engine 104 and transmission 106 of FIG. 1.The engine 104, electrical machine 102, and transmission 106 may bedriven by driveshaft 214 of FIG. 2. Various arrangements of the innerstage rotor 210, inner stage stator 208, outer stage rotor 204, andouter stage stator 202 can be used to place components closer or furtherfrom the central axis 216. Keeping components with a higher mass closerto the central axis 216 may affect the moment of inertia and otherdesign/performance parameters of the electrical machine 102.

Technical effects include providing cooling and lubrication for adriveline installable electrical machine with nested stages. The nesteddesign of the inner and outer stages of the electrical machine, whenused with the centrifugal reservoir geometry illustrated in FIGS. 2 and4, enables a high energy density electrical machine to be packaged witha shorter axial length. The combined use of positive displacement pumpsto provide suction with centrifugal pumping action of nested stagescreates a hybrid cascading lubrication and cooling system with highreliability to lubricate and cool an electrical machine.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A method for producing a hybrid cascading lubrication and coolingsystem (200, 400) for an electrical machine (102), the electricalmachine (102) comprising an inner nested stage (444) and an outer nestedstage (446), wherein the inner nested stage (444) is radially nestedabout a central axis (216) of the electrical machine (102) with respectto the outer nested stage (446), the method comprising: coupling an oilpump (222) to an oil pump inlet tube (226) to draw oil from an oil sump(224); configuring a cooling core (230) to distribute pumped oil withinthe electrical machine (102); and coupling a rotor member (212) to theinner nested stage (444) and the outer nested stage (446) of theelectrical machine (102), the rotor member (212) configured tocentrifugally pump oil from the cooling core (230) through inner radialholes (424) and outer radial holes (436) in the rotor member (212) uponrotation about the central axis (216) of the electrical machine (102).2. The method of claim 1 further comprising directing oil through a port(404) coupled to the cooling core (230) to a heat exchanger (406) of theelectrical machine (102).
 3. The method of claim 1 further comprisingdirecting oil through a port (408) coupled to the cooling core (230) toa first bearing (412) and a gear (414) of the electrical machine (102).4. The method of claim 3 wherein the port (408) supplies oil to acentrifugal reservoir (416), and the centrifugal reservoir (416)supplies a second bearing (418) with oil.
 5. The method of claim 3wherein the port (408) supplies oil to an inner stage centrifugalreservoir (420) of the inner nested stage (444).
 6. The method of claim5 wherein the inner radial holes (424) provide a flow path for oil fromthe inner stage centrifugal reservoir (420) through the inner nestedstage (444).
 7. The method of claim 1 further comprising coupling a port(410) to the cooling core (230), wherein the port (410) provides a flowpath to combine supplemental oil with oil from the inner nested stage(444) at an outer stage centrifugal reservoir (432) of the outer nestedstage (446).
 8. The method of claim 7 wherein the outer radial holes(436) provide a flow path for oil from the outer stage centrifugalreservoir (432) through the outer nested stage (446).
 9. The method ofclaim 1 further comprising coupling an oil pump outlet tube (228) to theoil pump (222) to route oil flow to a heat exchanger/relief valve/filterassembly (ERFA) (112), wherein the cooling core (230) receives oilreturned from the ERFA (112).
 10. The method of claim 9 furthercomprising: coupling a second oil pump (222) to a second oil pump inlettube (226) to draw oil from the oil sump (224); coupling a second oilpump outlet tube (228) to a second oil pump (222); and coupling a port(302) to the oil pump outlet tube (228) and the second oil pump outlettube (228) to combine oil flow from the oil pump (222) and the secondoil pump (222) prior to routing the oil flow to the ERFA (112).